In a large part of communication systems, data is transferred between a central unit and remote nodes. In the electrical power systems, for which this communication protocol was especially implemented, but not necessary limited, the electrical power meters should transmit to a central unit the data collected by them. In general this data includes: consumption, power demand, status information and various events. On the other hand the central unit distributes to the meters: Time of Use tables, tariffs and various load control commands.
In such cases the data transmission is performed via the Electrical power lines. These are the electrical utilities proprietary and the use thereof does not require a special permission, (as for radio), or installation of data cables.
However, communication quality of the electrical lines is low and changing in time, because of noises, changing electrical loads and changing line impedance. Due to these phenomena the communication range varies from several hundreds of meters to something like 80 m. or even less.
The communication network contains all the meters for a Low Voltage Network (LVN), which means all the meters connected to one transformer. The number of meters may differ from 8, in countries like USA, to several hundreds.
The distance from the remote units to the central unit may sometimes take 1600 meters and more.
This situation requires re-transmission of messages via a number of relays, in order to transmit a data between a remote node and the central unit.
A typical network may look like the one in FIG. 1. As can be seen the CU is connected to 3 phases of power line in the vicinity of the transformer. There are 2 branches going from the transformer to 2 different directions.
Theoretically, if we know the meter's topology, we may assume that the closer the meter is to the central unit, the better the communication between them. Consequently, for a given meter, we may choose relays that are on the same phase between it and the Central Unit, ensuring good communication. For example, the meter 5 may be used as a relay for meters 12 & 15 on the phase S and the meter 6 for meters 11, 14 & 18 on T.
Unfortunately, in practice, such topological information does not exist, and if it does, there is no guarantee that the above assumptions are true. A close node maybe a very poor relay, due to local load and noises, and very often nodes on different phases have better communication than these on the same.
Moreover, if the connection was successfully established, as for example 12 & 15 via 5, the removing of meter 5 will destroy it.
Contrary to the above, the communication protocol according to the invention does not require any previous knowledge of the meters topology. The only conditions for the remote node to be automatically added to the Central Unit data base, and to perform a permanent communication with it, is that it should have a communication with at least one other remote node, which is already connected. In this case the new RN will automatically be found, logged on and the route to it will be constantly improved. The route will be adopted to changing conditions in the network.
By employing the system according to the invention the following principles and advantages are achieved:
1. Automatic log-on of remote nodes, by joint of a route of a known node; PA1 2. Automatic mapping of a new installed Network, by recording all nodes together with their routes, reported as a part of message; PA1 3. Optimization of routes, using a Message Traveling Time factor; PA1 4. Creating dynamic routes to the central unit, by the Best Neighbor method; PA1 5. Creating dynamic routes by the CU, using the Best Neighbor method and according to a time period statistic; PA1 6. Combined Polling/Burst protocol, with dynamic Burst Period parameters; PA1 7. Helping the messages by re-transmitting them by hearing nodes; PA1 8. Controlling the traffic volume by reducing the data resolution.